地球历3588年，人类移居的类地行星戴尔曼星遭到了外星生命的猛烈攻击，人们使用了所有核武器摧毁外星战舰，却发现外星人留下了一种人类武器无法杀死的"巨虫"。巨虫吞噬着戴尔曼星的生命，以几何倍数迅速繁殖，不到半年，就占领了将近大部分陆地。人类被迫退居到面积狭小的海岛和人工浮岛，并重新建立了各自的国家。为抢夺匮乏的海上资源，各国经常发生战争......海上的人们深陷于内部的争夺中，似乎完全忘记了他们曾经拥有过的富饶的大陆。直到3821年，十四岁的莱斯利进入西兰军校，他在这里认识了达菲和一群热血，充满勇气的同伴，他们都有同一个目标使命：消灭巨虫，重夺属于人类的陆地。于是，他们肩负着这样的使命，成立了一支少年"海国战队"，一场正义的大战也即将开始...... ( During 3,588 years on the earth, Deilmann, a terrestrial planet in which humans migrated suffered a violent attack from extraterrestrial lives, people used all nuclear weapons to destroy the alien ships, but found that the aliens left a "giant insect" that humans weapon cannot kill. The giant insect devours the lives on Deilmann, and reproduces rapidly in geometrical multiples, in less than six months they occupied almost the majority of the land. Humanity was forced to the small area of sea island and artificial floating island, and re-established their own country. To scramble for the scarce marine resources, countries were often involved in wars......As people on the sea was trapped into wars, it seems that they had completely forgotten the rich continent they ever had.Until B.C. 3,821, the fourteen year old Leslie entered the Zealand Military Academy, where he met Duffy and a group of passionate and courageous companions, they all have the same goal and mission: destroy the giant insect, regain the land belonging to the human . Hence they shoulder such a mission setting up a juvenile "Sea World Team", a just war is about to begin ......)